After the carnage of the opening nine days, and a rest day that will still have been a little complicated by the long transfer from Brittany to the deep south of France, the Tour finally hits the mountains.

Given the varied route up until now, the organisers have kept the first climbing day relatively straightforward, with a long rolling route to the foot of a single mountain, at the top of which the stage will finish. And there’s one more bit of pertinent information about today’s stage: it’s Bastille Day, France’s national holiday. The French fans and media watch this stage a little more closely – there are few more popular events in the home nation than a French winner on July 14.

They have a good chance of success, too. In Thibaut Pinot, Romain Bardet, Pierre Rolland and Warren Barguil, the French have a golden generation of mountain climbers, with last year’s Tour runner-up Jean-Christophe Peraud also capable of matching the best at the Tour. If any of these riders, for any reason, is already out of the GC contest (with the exception of Barguil, who is at the Tour to gain experience and finish as high as possible without pressure), a stage win on La Pierre St Martin would rescue their race.

However, against the prospect of a home win is the fact that this is a crucial GC day. It’s not just the French riders who’ll realise how important a good result here is.

Tactical explainer

The structure of this stage might look straightforward – flat and rolling for 150 or so kilometres, then head skywards for the last 15. The perception might be that it would be easier to ride a stage like this than one containing multiple climbs before the summit finish. However, riders report that the change of rhythm, from riding along at 40-plus kilometres per hour, in the big chainring, to spinning a tiny gear up a steep hill, can play havoc with the legs. Add to this the fact that some riders’ bodies don’t respond well to Tour rest days, and this stage could turn out to be more complicated than anticipated.

The Col de la Pierre St Martin is a very hard climb. The average gradient is listed by the Tour organisation as 7.4 per cent for the 15 kilometres. That’s already hard - it’s over a kilometre longer than Alpe d’Huez, but only a little less steep – the Alpe averages 8.1 per cent. But the Pierre St Martin is fairly shallow for the last third of the climb – the average gradient of the first 10 kilometres is 8.7 per cent. A good climber in good form could do some real damage here.

Is this going to be a decisive day? The evidence points in both directions. The four Tours between 2008 and 2011 were all decided in the final mountain range, while in the three since then, the eventual winner has emerged by the end of the first day in the mountains. Lance Armstrong used to try and use the first mountain stage as a knockout blow, although whether that is good evidence any more is questionable. However, while a great deal of pre-Tour attention has focused on the fact that the opening nine days are so potentially decisive, it’s easy to forget that before the final 15 kilometres of this stage, we, and the riders themselves, will have no idea how the climbers and GC contenders are going. This stage should tell us a lot.

Bernard Thévenet's view

"It’s a difficult stage to ride. The first col of the first mountain stage in the Tour is always complicated. The riders have spent over a week riding very fast in a big gear, and suddenly they have to be in the small ring, spinning their legs fast. Physiologically, it’s a very different challenge and some riders adapt more easily to it than others. Some riders need time to get used to it.

"Nobody really knows where they are until they actually ride a mountain, so this climb is a dangerous place. The Pierre St Martin is a very high and hard climb. It’s not easy at all."

Stats & Facts

This is the first time the Tour has had a stage finish on the Col de la Pierre St Martin and the first time the race has climbed the col from the French side.